Plastic bottles with dispensing closures or bottle caps are the chosen packaging for a broad range of products such as shampoos, conditioners, hand lotions, household detergents, cleaning products and contact lens solutions, to list a few of a vast menagerie of products. They abound and pervade our everyday existence.
Normally, the dispensing closures are mounted on the neck of the bottles by inter-engaging screw threads or a snap on arrangement characterized by a frictional fit.
Dispensing closures are generally of single wall or double wall construction. Single wall closures have one side wall of a generally cylindrical shape. Double wall closures are characterized by a double sidewall arrangement having interior and exterior sidewall of generally cylindrical shape. If threaded engagement means are utilized in a double side wall closure, the threads are located upon the interior side of the interior cylindrical sidewall (see FIG. 7, depicting this prior art closure).
The choice of closure, whether it be double or single wall construction, directly affects the design and manufacturing parameters of the mating plastic bottles. Double wall closures necessarily have bottle necks of reduced size, requiring a high blow ratio in bottle manufacture. This means that if a double wall closure is chosen, the volume of the bottle itself is limited. On the other hand, single walled closures can be designed with larger necks and are thus moldable into larger sizes and shapes.
In addition to practical design considerations, as for example, bottle size, other less obvious factors are of significance. Those who manufacture plastic bottles, and those who package product in plastic bottles have justifiable concerns regarding the aesthetics of the packaging. It is important that product packaging be pleasing to the consumer as this is the source of initial introduction of the product to the consumer. Thus, the container designer should consider and employ available means of visually enhancing the package.
One such means is disclosed in U.S. Pat. No. 4,877,144 which is incorporated herein by reference. This patent discloses a bottle closure having a segmented external thread that is molded so as to eliminate the occurrence of mold markings on the exterior wall of the threaded sleeve.
With respect to snap hinge closures having a thumb recess for facilitating the lifting of the lid, another consideration is to position the thumb recess so that it is centered upon the wider side of a bottle having an oval or elliptical cross section. This is referred to as positive alignment. Besides the aesthetic enhancement provided by the symmetry, the consumer benefits from a more convenient access to the recess. This has been achieved for double walled closures, but no such positive alignment means are known for single walled closures. This represents a substantial deficiency in the technology, since single walled closures permit the bottle to be of larger size.